<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
  
</head>
<body>
   <input type="button" value="测试" name="" id="" onclick="javascript:alert('我是javascript')">

  
   <script>
       var width = 5;
       alert(width)
   </script>
</body>
</html>